This invention relates to terminal perfluoroalkylsilane compounds, methods of preparing these compounds, and coating agents using such compounds.
Conventional terminal perfluoroalkylsilane compounds were manufactured as follows. For instance, such perfluoroalkene compound as C.sub.4 F.sub.9 CH.dbd.CH.sub.2 or C.sub.8 F.sub.17 CH.dbd.CH.sub.2 is allowed to react, with platinum as catalyst and through hydrosilylation, with HSi(CH.sub.3)Cl.sub.2 or HSiCl.sub.3 to synthesize into terminal perfluoroalkylsilane C.sub.4 F.sub.9 (CH.sub.2).sub.2 Si(CH.sub.3)Cl.sub.2 or C.sub.8 F.sub.17 (CH.sub.2).sub.2 SiCl.sub.3. The terminal perfluoroalkylsilane compounds obtained by the above process are however limited to compounds of ten or less carbon atoms in the fluoroalkyl group bonded to silicon atom. The perfluoroalkene compounds may be produced as intermediate products or byproducts in the process of fluorocarbon resin industry.
Magnetic recording materials of mediums as magnetic disks or tapes have magnetic film applied with coating agent on the surface of which a lubricating layer is formed. This is however problematical because the capability of the lubricating layer may be reduced due to its deviation, splashing and/or evaporation thereof by displacement of coating agent. Though diverse coating agents to be applied under low vapor pressure have been used for that reason, this could not lead to a drastic resilution of the problem.
As the compounds having fluoroalkyl groups have been observed to be excellent in lubricity, the inventors of the present invention performed a study for forming a lubricating layer on a magnetic film applying terminal perfluoroalkylsilane compounds as coating agents, thereon. Use of conventional terminal perfluoroalkylsilane compounds cannot give a satisfying lubricating effect though. Further such defects were discovered as unevenness and pinholes on the lubricating layer and/or poor durability thereof. As a result of thorough investigations and studies of the reasons of the defects, it has eventually been revealed the following. Terminal perfluoroalkylsilane compound, sillane coupled with an inorganic substance on the magnetic film, forms a monomolecular film. However, the conventional terminal perfluoroalkylsilane compounds cannot form a uniform film when used as a coating agent since the compounds have only ten or less carbon atoms in their fluoroalkyl group bonded to the silicon atom, as mentioned above. It is conceivable that the abovementioned defects of insufficient lubricating effect may be caused.
Inventors of the present invention anticipated that if a fluoroalkyl group bonded to the silicon atom being long enough in a terminal perfluoroalkylsilane compound, it would be excellent as a coating agent. But there never existed terminal perfluoroalkylsilane compounds meeting such a condition. Moreover, perfluoroalkene compounds, which were intermediate products for synthesizing terminal perfluoroalkylsilane compounds, never had long enough chain molecules. In addition, the number of fluorine in the perfluoroalkene compounds have been limited.
The inventors took up a presupposition as below.
First, a terminal perfluoroalkyl compound F(CF.sub.2).sub.m (CH.sub.2).sub.n X.sup.1 (X.sup.1 is I, Br or Cl) with longer chain molecules could be synthesized from starting material of available terminal perfluoroalkyl compound having relatively short chain such as F(CF.sub.2).sub.2 CH.sub.2 I, F(CF.sub.2).sub.2 CH.sub.2 Cl, or F(CF.sub.2).sub.3 I. Then Grignard's reagent F(CF.sub.2).sub.m (CH.sub.2).sub.n MgX.sup.1 would be synthesized therefrom. This reagent, when allowed to react with (CH.sub.3).sub.p SiX.sup.3.sub.4-p (p is an integral number between 2 and 4, X3 is I, Br, Cl or alkoxyl group), would lead to a synthesis of a terminal perfluoroalkylsilane compound having longer chain. Although the inventors tried the experimentation of this process of the presupposition. Grignard's reagent could not be stably synthesized from the F(CF.sub.2).sub.2 CH.sub.2 X.sup.1, F(CF.sub.2).sub.3 X.sup.1 nor from F(CF.sub.2).sub.m (CH.sub.2).sub.n X.sup.1. Therefore, a terminal perfluoroalkylsilane compound having long chain molecules of fluoroalkyl group could not be synthesized.